1. Field of the Invention
This invention relates to circuitry that provides voltage and current to a microprocessor such that the voltage from a power source can be pulled down to thereby provide more current to the microprocessor and related circuitry. More particularly, this invention relates to circuitry which lowers the operating voltage of microprocessor circuitry to thereby increase current to the same circuitry and maximize the clock speed of the microprocessor circuitry.
2. Description of the Related Art
Most microprocessors and co-processors function using a fixed clock rate. The fixed clock rate is generally generated by a crystal oscillator. As microcircuits decrease in size and as the packages that microcircuits are placed in become smaller and smaller, a crystal oscillator will not fit in the packages because they are too large. Fixed crystal oscillators are generally used to properly time microprocessor-related operations. Such fixed crystal oscillators, in combination with a microprocessor, generally require a steady voltage and a steady current source to operate correctly and maintain the fixed operating clock frequency.
A ring oscillator circuit can be used in place of a fixed crystal oscillator. A ring oscillator can be used when the microprocessor is being used as a "number cruncher," that is, used to perform mainly mathematical functions without a need to operate time-related functions. Number crunching microprocessors and co-processors generally are concerned with the speed at which a calculation can be completed. Thus, the faster the ring oscillator runs, the higher the clock frequency and the faster the circuitry can "crunch numbers."
Using a ring oscillator to act as the oscillator for a microprocessor or co-processor is not new. Ring oscillators have been used for years. Ring oscillator circuitry can be smaller than a crystal oscillator. However, a fixed frequency ring oscillator is what is generally used. A drawback of a fixed frequency ring oscillator is that it must have a dependable constant current source in order to maintain its fixed frequency. If the current source to the circuitry is variable, the fixed frequency ring oscillator cannot function properly.
In a device where the power used by the device is provided by an outside source, the voltage and current supplied by the outside source or "host" may vary from host to host. That is, different hosts will provide different voltages and currents for the device's operation. Thus, a microprocessor-based device that, for example, is adapted to be connected to a variety host power sources must be able to operate with different voltage and current supplies available from the different hosts.
Voltage and current are related by the equation: Power=(Voltage) (Current). Thus, given a fixed amount of power from a host circuit, current can be increased by lowering the voltage. If enough current is supplied by a host to a microprocessor, then the voltage can be left alone.